sed replace all tabs and spaces with a single space

linux domain-name-system bash sed dig

185

Solution 1

Use sed -e "s/[[:space:]]\+/ /g"

Here's an explanation:

[   # start of character class

  [:space:]  # The POSIX character class for whitespace characters. It's
             # functionally identical to [ \t\r\n\v\f] which matches a space,
             # tab, carriage return, newline, vertical tab, or form feed. See
             # https://en.wikipedia.org/wiki/Regular_expression#POSIX_character_classes

]   # end of character class

\+  # one or more of the previous item (anything matched in the brackets).

For your replacement, you only want to insert a space. [:space:] won't work there since that's an abbreviation for a character class and the regex engine wouldn't know what character to put there.

The + must be escaped in the regex because with sed's regex engine + is a normal character whereas \+ is a metacharacter for 'one or more'. On page 86 of Mastering Regular Expressions, Jeffrey Friedl mentions in a footnote that ed and grep used escaped parentheses because "Ken Thompson felt regular expressions would be used to work primarily with C code, where needing to match raw parentheses would be more common than backreferencing." I assume that he felt the same way about the plus sign, hence the need to escape it to use it as a metacharacter. It's easy to get tripped up by this.

In sed you'll need to escape +, ?, |, (, and ). or use -r to use extended regex (then it looks like sed -r -e "s/[[:space:]]\+/ /g" or sed -re "s/[[:space:]]\+/ /g"

Solution 2

You can use the -s ("squeeze") option of tr:

$ tr -s '[:blank:]' <<< 'test.de.          1547    IN      SOA     ns1.test.de. dnsmaster.test.de. 2012090701 900 1000 6000 600'
test.de. 1547 IN SOA ns1.test.de. dnsmaster.test.de. 2012090701 900 1000 6000 600

The [:blank:] character class comprises both spaces and tabs.

185

Premt

Updated on September 18, 2022

Comments

Premt almost 2 years

Hi guy's i got this math equation to movement the enemy x,y,z but i can't seem to replicate the result i want once am done with x,y i wanna create z movement also

So let's say i have a enemy with the movement speed of 1.5 his position is

Enemy Position: posX > 119.75013, posY > 12.1830482, posZ > 167.700226

I want to move him to

Enemy Final Position: posX > 119.41893, posY > 11.3724937, posZ > 162.9639

With these x,y,z result:

Enemy movement: posX > 119.645088, posY > 11.9535465, posZ > 166.198029
Enemy movement: posX > 119.539749, posY > 11.7193651, posZ > 164.691589
Enemy movement: posX > 119.479477, posY > 11.54633, posZ > 163.829742

But the function only prints

Enemy Movement: posX 119.182753804649, posY 10.7944934646909

Note i am not using Unity3D so i need a function that works with out unity3d..

Current function:

static void Main(string[] args)
{
    double startX = 119.75013;
    double startY = 12.1830482;
    double startZ = 167.700226;

    double x = 119.41893;
    double y = 11.3724937;
    double z = 162.9639;

    double endX = x;
    double endY = y;
    double endZ = y;

    double speed = 1.5f;

    Console.WriteLine($"Enemy Position: posX {startX}, posY {startY}, posZ {startZ}");
    Console.WriteLine($"Enemy Final Position: posX {x}, posY {y}, posZ {z}\n");

    double distance = Math.Sqrt(Math.Pow(endX - startX, 2) + Math.Pow(endY - startY, 2));
    double directionX = (endX - startX) / distance;
    double directionY = (endY - startY) / distance;


    double newlat = startX;
    double newLng = startY;


    while (Math.Sqrt(Math.Pow(newlat - startX, 2) + Math.Pow(newLng - startY, 2)) <= distance)
    {

        newlat += directionX * speed;
        newLng += directionY * speed;

        Console.WriteLine($"Enemy Movement: posX {newlat}, posY {newLng}");
    }

    Console.ReadKey();
}

Thank you!

RJS almost 12 years

Try: sed -r -e "s/[\t\ ]+/ /g"
rory.ap about 7 years

This question will be closed as off topic unless you can improve it. . Questions which ask "why isn't this code working" are off topic unless they contain more information. Please go to How to Ask and help center.
Premt about 7 years

Okay edited ty.
Jeroen van Langen about 7 years

There is no z movement in your code. So the z won't be affected
Premt about 7 years

I know z won't be effected i need to get the results of x,y right first to make the z .
Franck about 7 years

If you don't want to use Unity i highly suggest you check out System.Windows.Media.Media3D namespace. Point3D and Vector3D can do most of the work.

Zulakis almost 12 years

Does this remove tabs too? Can you explain why you use \+ instead of just +?
Zulakis almost 12 years

Okay, I understand. [[:space:]] is equal to [ \t\r\n\v\f]. But can you please explain why you use \+
SiXoS almost 12 years

[[:space:]] is equivalent to '\s', so the shorter version is "s/\s\+/ /g"
SiXoS almost 12 years

Basic regular expressions use a backslash prior to a plus sign when used to mean “one or more of the previous character or group”, source developer.apple.com/library/mac/#documentation/opensource/….
Zulakis almost 12 years

Ahh, I understand! I did not know that there were different regex versions. Thanks
Jeroen van Langen about 7 years

You must change the newlat - startX to endX - newlat Same for newLng - startY to endY - newLng You're subtracting the old value from the new value. But instead you still want the delta between te new position and the endpoint. You should use the Vector3 types/math. way easier..
Premt about 7 years

Don't really get how i can apply this to my code can you apply it so i understand?
Aziuth about 7 years

@Premt You... exchange double speed = 1.5f; with double speed = 0.25f;. But please, do not use code that you don't understand!
Læti about 7 years

How does this answers the question?
UpAndAdam over 4 years

This seems wrong. at least on OSX I have to do `sed -E "s/[[:space:]]+/ /g" when we go to extended you dont need to escape the + sign for multiplicity anymore.